The present invention relates to a rotation stabilizing device that stabilizes rotation by inhibiting fluctuations of rotation, a rotation driving mechanism equipped with the rotation stabilizing device, an image forming apparatus wherein rotation fluctuations of an image carrier such as a photoreceptor drum can be inhibited, and to an image reading apparatus.
In recent years, there is a demand for stabilization of driving technologies in various technical fields. For example, there is known a technology to arrange a damper to stabilize driving of a motor that is used to drive a photoreceptor drum and a transfer belt both serving as an image carrier of an image forming apparatus such as a copying machine of an electrophotographic system and a printer. The photoreceptor drum of the image forming apparatus needs to be driven at a constant speed, and therefore, if speed fluctuations occur, image quality is deteriorated. The speed fluctuations are caused by fluctuations of a load applied on the image carrier, and the load fluctuations are not always regular in terms of their size and cycle. It has been impossible, therefore, to change a driving force for the image carrier by predicting load fluctuations.
Without being limited to the image forming apparatus, various technologies have been employed to stabilize driving of a rotating object. For example, it is known that a damper is arranged to achieve stabilization for driving a motor. In TOKKAISHO No. 61-9156, a damper is disclosed for a stepping motor wherein a flange portion fixed on the motor shaft is united with an inertia object through an elastic member.
In this conventional example, however, it is not possible to change a position, the number and a material of the elastic member, nor the dimensions and materials of the flange portion and the inertia object, because the inertia object is fixed to the flange portion and to the inertia object by means of adhesive agents or through a method of baking, resulting in a damper that is not versatile and has a low degree of freedom in use. Accordingly, it is impossible to replace the elastic member and the inertia object even when they have deteriorated, which requires an entire damper to be replaced. In this way, those having the conventional structure are not versatile, and other types need to be prepared in advance, which causes a cost increase.
An object of the invention is to provide a rotation stabilizing device that has versatility for use and a high degree of freedom and can inhibit rotation fluctuation and stabilize the rotation, and a rotation driving mechanism, an image forming apparatus as well as an image reading apparatus all having therein the rotation stabilizing device.
For attaining the object stated above, the rotation stabilizing device of the invention has therein a rotating member that rotates about a central axis for rotation, an inertia member arranged on at least one of an outer circumferential side and an inner circumferential side of the rotating member, and a combining member that is equipped with a visco-elastic member having viscosity and elasticity and combines the rotating member with the inertia member in a detachable manner through the visco-elastic member, wherein the combining member is mounted in a way that the combining member passes through the rotating member and the inertia member in the radial direction of the central axis for rotation.
In the case of the rotation stabilizing device wherein fluctuations of rotation speed of the rotating member are controlled by vibration of the inertia member and the visco-elastic member having viscosity and elasticity changes its shape in accordance with the vibration of the inertia member, even when vibratory force that causes fluctuations of rotation speed on the rotating member is generated, the fluctuations of rotation speed are controlled and the rotating member can rotate stably. Further, it is easy to replace the visco-elastic member, the rotating member and the inertia member, because the combining member combines the rotating member and the inertia member in a detachable manner, and various members can be combined freely to make adjustment for rotation stability to be easy, thus, the rotation stabilizing device which is versatile and has a high degree of freedom in use can be realized. Further, because of a simple structure, it is possible to realize a rotation stabilizing device that is low in cost and is durable in structure. It is further possible to construct the rotation stabilizing device that is compact in the axial direction, because it is possible to mount inertia members on the rotating member on the equal phase basis in the axial direction of the central axis for rotation.
Further, in the case that the inertia member is provided at an outer periphery side of the rotating member, the inertia member can be approached from a direction perpendicular to the shaft. Accordingly, it may become easy to conduct attaching/detaching or adjusting the inertia member from the direction perpendicular to the shaft. Further, by providing the inertia member at the outside of the rotating member, a relatively large inertia moment can be obtained easily with a relatively light inertia member, whereby it become possible to make the weight lighter and to refrain fluctuation in a rotating speed.
By providing a rotary shaft that is united with the rotating member fixed on the rotating member and rotates together with the rotating member, the rotary shaft can be connected to a rotary shaft of a motor, thus, it is possible to mount the rotation stabilizing device on the motor.
Further, when the combining member is provided with a connecting member that mounts the visco-elastic member on both the rotating member a nd the inertia member, it is easy to mount the visco-elastic member.
A flange portion formed to be solid with the visco-elastic member makes it possible for the connecting member to mount the visco-elastic member on the rotating member and on the inertia member. In this case, it is preferable to construct so that the flange portion of the connecting member may be interposed between the rotating member and the inertia member.
It is further possible for the connecting member to be supported by a supporting portion provided on at least one of the rotating member and the inertia member. In this case, it is preferable that the connecting member is screwed on or fitted with the supporting portion. It is further preferable that the connecting member is inserted into the through hole provided on the visco-elastic member and is supported by the supporting portion.
Further, it is preferable that the rotating member is constructed to be in a disk-like shape or in a cylindrical shape, and the inertia member is constructed to be in a disk-like shape or in a cylindrical shape. In this case, it is possible to construct so that the inertia member and the rotating member are arranged to be concentric each other. Incidentally, the disk-like shape in the present specification means a shape viewed on a plane that is perpendicular to the direction of the central axis for rotation, and it is represented by a flat shape.
It is further preferable that the mounting position for the combining member can be adjusted to the position selected optionally from a plurality of positions in the circumferential direction and a plurality of positions in the axial direction. The foregoing makes it possible for the mounting position of the combining member to be adjusted in accordance with the number of vibrations to be lowered, thus, it is possible to cope with the broader range of frequency and to realize a rotation stabilizing device which further stabilizes rotation.
By providing a plurality of holes through which the visco-elastic member is mounted on either one of the rotating member and the inertia member, the mounting position can simply be adjusted. In this case, it is preferable that holes in the circumferential direction are provided at positions arranged at regular intervals. It is further preferable to arrange a plurality of combining members.
The rotation driving mechanism of the invention is provided with a rotating member that rotates on a central axis for rotation, an inertia member arranged on at least one of an outer circumferential side and an inner circumferential side of the rotating member, and a combining member that is equipped with a visco-elastic member having viscosity and elasticity and combines the rotating member with the inertia member in a detachable manner through the visco-elastic member, wherein the combining member is provided with a rotation stabilizing device that is mounted to pass through the rotating member and the inertia member in the radial direction of the central axis for rotation, a rotation driving means, a rotary shaft that is rotated together with the rotating member by the rotation driving means and a rotation transmission mechanism connected with the rotary shaft.
In the rotation driving mechanism, fluctuations of rotation speed of the rotating member are controlled by vibration of the inertia member, and the visco-elastic member having viscosity and elasticity changes its shape in accordance with the vibration of the inertia member, thus, even when vibratory force that causes fluctuations of rotation speed on the rotation driving means is generated, the fluctuations of rotation speed are controlled and the rotating member of the rotation stabilizing device can rotate stably, resulting in stable rotation of the rotary shaft and transmission of stable rotation from the rotary shaft. Further, it is easy to replace the visco-elastic member, the rotating member and the inertia member, and various members can be combined freely, because the combining member of the rotation stabilizing device combines the rotating member and the inertia member in a detachable manner. It is further possible to construct the rotation driving mechanism on a compact basis in the axial direction because inertia members can be mounted on the rotating member on the equal phase basis in the axial direction of the central axis for rotation.
In this case, it is preferable that the rotation stabilizing device is further provided with a rotary shaft on the rotation stabilizing device side that is rotated together with the rotating member fixed on the rotating member and is connected to the rotary shaft.
It is further possible to arrange so that the rotation driving means is equipped with a rotary drum, and the rotating member of the rotation stabilizing device is constructed integrally with the rotary drum. In this case, an inertia member is combined with the rotary drum such as a rotor of the motor through the visco-elastic member.
Further, the rotation transmission mechanism may be provided with a timing belt pulley connected with the rotary shaft, a timing belt that engages with the timing belt pulley and with a timing belt pulley that engages with the timing belt provided on a driven portion. The rotation transmission mechanism may also be provided with a first gear connected with the rotary shaft and a second gear that is provided on the driven portion and engages with the first gear. Incidentally, in this case, the pulley and the gear may also be constructed to be integrated solidly with the rotating member of the rotation stabilizing device.
An image forming apparatus of the invention is provided with a rotating object which is equipped with an image carrier that carries an image formed by an image forming means, an inertia member arranged on the outer circumferential side of the rotating object and a combining member that is equipped with a visco-elastic member having viscosity and elasticity and combines the inertia member with the rotating object through the visco-elastic member on a detachable manner, and wherein the combining member is mounted to pass through the rotating member and the inertia member in the radial direction of the rotating object.
The image forming apparatus wherein an inertia member is mounted on a rotating object such as a photoreceptor drum through a visco-elastic member makes it possible to inhibit rotation fluctuations of an image carrier with a simple structure, and to stabilize rotation for obtaining excellent image quality. Further, an inertia member provided on an outer circumferential side of a rotating object makes the structure to be compact in the axial direction of the rotary shaft, which contributes to space saving of the image forming apparatus.
Further, for example, by providing a rotation driving mechanism equipped with the above-mentioned rotation stabilizing device is provided on a photoreceptor drum serving as an image carrier of an image forming apparatus, a transfer belt, a transfer drum or a cleaning unit, or on an image reading section of an image reading apparatus, it is possible to inhibit rotation fluctuations through the simple structure and to stabilize the rotation. By virtue of this, excellent image forming or image reading can be made possible, and excellent image quality can be obtained.